I agree that Mence does not fall under the Offensive Characteristic because its easily revenged killed... but that's where the problem lies... he's easily revenged killed... by moves that don't really hurt other pokemon.
So lets look at the stuff that revenges Mence with little harm to themselves. CB Scizor, Scarf Jirachi, Scarf Latias, Weavile, Mamoswine among others, but these are the ones that this thread is consistently bringing up. Now... Scizor has to use Bullet Punch, Scarf Jirachi has to use Iron Head / Ice Punch. ScarfLatias has to use Draco Meteor and ice shard for mamo/weavile. None of these are powerful moves by any means, and some of the pokemon are just not powerful (Weavile, Jirachi). Making them easy setup bait. Don't try to deny that the second you kill a Mence, a resist to whatever move you used will come in and attemp to set up, and more than likely get it done. This is where the Support Characteristic comes into play, as remember
you have to sacrifice a pokemon to revenge Mence
Support Characteristic
A Pokémon is uber if, in common battle conditions, it can consistently set up a situation in which it makes it substantially easier for other pokemon to sweep.
This is why DD Mence + SD Luke is such a potent combo. SDLuke is just an example among others though, but Mence creates the most likely situation where Lucario will sweep. Gyarados, AgiliGross, Empoleon, SubCharge Magnezone ANYTHING that can set up on a steel type move can and will if DDMence is revenged. And due to DDMence bringing in Swampert and other bulky waters and OHKOing/Substantially damaging them, these pokemon are near impossible to stop after a DDMence rampage is over. So who cares if Mence can be revenged, the moves it is revenged by are weak enough for others to take advantage of e.e.
SR plus checks that force Mence out means that it takes quite a bit of effort to sweep with Mence. That is what disqualifies Mence from Uber.
Um bullshit? How do we know that Mence hasn't caused every to have a reason to need SR / Checks? This is why a test would be nice.
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tl;dr mence fits the support charicteristic imo. test would be cool.